SUMMARY The visceral leishmaniasis (VL) elimination strategy in the Indian subcontinent, that has a current goal of reducing the incidence of VL to below 1/10,000 people by 2017, consists of rapid detection and treatment of VL cases to reduce the number of human infection reservoirs, and vector control using indoor residual spraying (IRS). To achieve sustained elimination of VL, an appropriate surveillance program is needed to detect the emergence of insecticide resistant populations of P. argentipes, as well as studies to define the contribution of individuals from across the infection spectrum, and of possible non-human reservoirs, to the maintenance of the L. donovani transmission cycle. To address these issues, we have proposed a series of cutting edge studies that will exploit the exceptional resources now available to carry out vector related research in Bihar. These resources include 1) a new, fully functional insectary that will permit containment, rearing, infection, and manipulation of field caught sand flies, 2) an established working colony of P. argentipes that has been certified for use in xenodiagnostic procedures, and 3) an entomological field team that has extensive experience in the capture, taxonomic identification, and colonization of sand flies in Bihar. Studies are proposed to survey insecticide resistance in field populations of P. argentipes, establish a pyrethroid resistant colony, and develop biomarker-based assays to quickly identify emergent populations of insecticide resistant sand flies in Bihar. Vector competency studies will be conducted on wild caught P. argentipes captured from different peridomestic settings and associated to their midgut microbiota profiles. Methods for metagenomic sequencing and analysis will interface with the studies of the human gut microbiome proposed in Project 1. Cultivable bacterial flora that appear to negatively or positively impact Leishmania development will be used in bacterial feeds in attempts to manipulate vector competence in colonized flies. The colonized flies will also be used in xenodiagnostic assays to identify possible non-human reservoirs that may be playing a greater role in the maintenance of the L. donovani transmission cycle as a consequence of IRS. Finally, the metabolic and immunologic profiling approaches proposed in Projects 1 & 3 will be applied to the ongoing human xenodiagnostic surveys sponsored by the Gates Foundation in attempts to identify biomarkers in plasma and localized sand fly bite sites that are associated with transmission potential in infected people.